Question

In: Chemistry

Consider a 0.487 L solution of the amino aspartic acid (0.685 M), which ahs a carboxylic...

Consider a 0.487 L solution of the amino aspartic acid (0.685 M), which ahs a carboxylic acid group (pKa = 2.10), an amine group (pKa = 9.82), and a carboxylic acid side chain (pKa = 3.86). How many liters of 2.59 M NaOH would you need to add to reach the isoelectric point of the amino acid?

Solutions

Expert Solution

ANS)           given side chain   Pka =3.86 ,acidic group Pka = 2.10

                         isoelectric point ( PH) = 3.86 + 2.10 / 2   =   2.98

                   NaOH     + ASPARTIC ACID    ------------      SALT   + H2O

      mole added         2.59* V                  0.487 * 0.685=0.3335                 0             0

     moles after rxn          0                     0.3335 -   2.59V                           2.59V           2.59V

                               [ ACID ] = 0.3335 -2.59V / 0.487+ V   , [ SALT ] =   2.59V / 0.487+ V

                         USING Hendersons eq     PH = PKa   + log [ salt ] / [acid ]

                                                        2.98   =   2.10 + log [ 2.59V / 0.487+ V]   /   [ 0.3335 - 2.59V / 0.487 +V

                                                  0.88 = log 2.59v+ 0.4749 + log 2.59v

                                           v =0.2364 L

                                  thank u


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